Android: Sometimes showing is better than telling. Why not do both? Clarisketch lets you share a picture, with drawn-on annotations, and even includes your own descriptions as you say them.

Clarisketch allows you to create a recording of an image, so you can annotate the parts of the picture you want to draw attention to. It also records your narration automatically when you speak, so you can describe what you're looking at while you work. When you're ready to share, the video gets uploaded to Clarisketch's servers. Anyone with the link can then see your image played back in real time as it was made.